482 



Messrs. Carpenter, Jeffrey s, and Thomson (Nov. 18, 



of his 'Elements of Chemistry.' It was found necessary to make se- 

 veral modifications in it, to adapt it to the motion of the vessel. These 

 consisted chiefly in suspending much of it from the cabin-ceiling, instead 

 of supporting it from beneath, and in rendering all the parts less rigid 

 by a free use of caoutchouc tubing, &c, the utmost care being taken to 

 keep all joints tight. 



It was found possible to make correct analyses, even when the vessel 

 was rolling sufficiently to upset chairs and cabin-furniture. 



The method of Analysis may be thus summarized : — From 700 to 800 

 cubic centimetres of the sample to be examined were boiled for about 30 

 minutes, in such a way that the steam and mixed gases evolved were col- 

 lected over mercury in a small graduated Bunsen's Gas-holder, all access 

 of air being carefully guarded against. The mixed gases were then trans- 

 ferred to two graduated tubes in a mercurial trough, where the Carbonic 

 Acid was first absorbed by a strong solution of caustic potash ; and subse- 

 quently the Oxygen was absorbed by the addition of pyrogallic acid, the 

 remaining gas being assumed to be Nitrogen. 



The results of the analyses were always corrected to the standard Tem- 

 perature of 0° Cent., and to 760 millimetres Barometric pressure, for com- 

 parison among themselves and with others. In nearly every case the du- 

 plicate analyses from the same gaseous mixture agreed closely, if they were 

 not identical. 



(3) The examination of the Sea-water for Organic matter was made ac- 

 cording to the method detailed by Prof. Miller in the Journal of the Che- 

 mical Society for May 1865, with an addition suggested by Dr. Angus 

 Smith. Each sample of water was divided into two; to one of these a 

 little free acid was added, and to both an excess of a standard solution of 

 Permanganate of potash. At the end of three hours the reaction was 

 stopped by the addition of Iodide of potassium and Starch, and the excess 

 of Permanganate estimated by a standard solution of Hyposulphite of soda. 

 The portion to which free acid was added gave the Oxygen required to 

 oxidize the decomposed and easily decomposable organic matter; the second 

 portion gave the oxygen required by the decomposed organic matter alone, 

 which was usually from about one-half to one-third of the whole. 



The following is a Summary of the total number of observations, ana- 

 lyses, &c. made during the Three Cruises respectively : — 





First 

 Gruise. 



Second 

 Cruise. 



Third 

 Cruise. 



Total. 



Specific-Gravity determinations . 





*7 



26 



125 





45 





21 



89 





137 



26 



3* 



195 



